Do Heat Pumps Deliver?

Do heat pumps actually deliver the energy and carbon savings that housing professionals and energy assessors predict?  A study by the Energy Saving Trust (EST) appears to show that they don't.

The measure of the performance of a heat pump is the coefficient of performance (COP).  This is the ratio of the heat energy that it delivers to the electrical energy that the unit consumes to do so.  An electric fan heater or storage heater would have a coefficient of performance of 1.0 - every unit of electricity consumed in the device ends up as a unit of heat energy in the building.  Heat pumps use electricity more intelligently than this, driving a condensation cycle which cools the ground or air outside a building and delivers the energy as higher temperature heat inside.  The technology is similar to a refrigerator, which transfers heat from inside the fridge to the room outside using the same principle.

For a heat pump to produce a carbon saving relative to a gas-fired boiler in the UK, it needs to be operating at a COP higher than 2.35.  This is because grid electricity has a high carbon-intensity.  When you consume a unit (kWh) of electricity, 0.52kg of carbon dioxide are emitted at a power station.  When you use a gas boiler to produce a unit of heat for your home, around 0.22kg of carbon dioxide are emitted from its flue.

70% of homes would have had lower carbon emissions with a gas boiler

The chart above shows the range of COPs measured in the EST trials (white) compared to the range of COPs claimed by manufacturers (orange) and used to calculate household energy for building regulations.

Fully 70% of households in the EST field trial would have lower carbon emissions from heating their properties if they had instead selected much cheaper gas-boilers.  It also appears that building regulations calculations are over-stating the efficiency of heat pumps by around 60% compared to the real-life examples in the trial.

Can any professionals from heat pump companies offer an explanation for the EST trial results, or highlight errors in this analysis?  Please leave your comments below.  Check workings here if you like.

Solar Heating - Could Do Better - UK Ranks Lowest Among Major European Economies

The United Kingdom ranks last for solar heating installations among its european peer group.  Germany has installed twenty times more solar heating per head of population, and Austria sixty times more, figures from the Euroobserv'er 2011 Barometer show.



The chart above shows the amount of solar heating panels installed in each of the major economies in Europe per head of population.  The wide range is only partly driven by climate, with many northern european countries scoring among those with the highest installed base.

A spreadsheet with sources, data for all European countries and calculations can be found here.

After the Party - UK PV Industry in 2011

How to build a sustainable industry

The UK photovoltaic solar installation industry returns to work in 2012 with the mother and father of all hangovers.

The chart shows the amount of solar photovoltaic capacity added each week in megawatts during 2011. 

On October 31st, the Department of Energy and Climate Change (DECC) launched a consultation on the Feed in Tariff (see earlier blog post here).  Alarmed by the rate at which solar installations were using up the allocated budget, DECC also announced that tariff levels were to be cut by more than half from December 12th.

A sprint to the line ensued, with 382MWp installed in the six weeks leading up to the deadline - more than the total since the Feed in Tariff scheme began in April 2010.  In the last week before the cut, 126MWp was installed and commissioned - sixteen times the rate of installation through the summer.

Unfortunately, the finishing line for this race was set up on a cliff edge.  The week after the deadline, installations fell 98% to only 2MW.

It remains to be seen what the long term impact on PV businesses will be.  This deadline was always going to pull forward installations, suppressing demand for a time afterwards. 

However, scaling up a business by sixteen-fold over a few weeks while at the same time maintaining the quality of solar installations would appear to be a ferociously difficult challenge.  We must hope that this challenge was met; else it could damage the reputation of an industry for years to come.

Slippery When Watt

Don’t know your megawatts from your kilowatts peak?  You’re not alone.  Look no further for help.

What’s a Watt?

Some watts are more equal than others

The watt is the unit of power – the rate at which energy is converted from one form, for example coal, to another, for example electricity in a power station. 

According to its rating plate, my kettle at home converts electrical energy to heat energy to keep us going in tasty hot beverages at the rate of 2.2 kilowatts, or 2,200 watts.

1 kilowatt (kW) = 1,000 watts.

At the other end of the scale, my nearest power station at Little Barford, is busy keeping the nation’s television screens alight by burning natural gas to make electricity at the rate of 680 megawatts, or 680,000,000 watts – enough to run 300,000 of those kettles at the same time.

1 megawatt (MW) = 1,000,000 watts.
So if you read that 650 megawatts of photovoltaic solar panels were installed under the Feed in Tariff during 2011, you can compare this to a power station in terms of energy output.  Right?  Wrong!

Give me a ‘p’
A fossil fuel fired power station could in theory run day and night every day of the year at or near full rated output.  The decision whether to or not is typically economic, or influenced by down time for maintenance.

In contrast, a photovoltaic solar panel makes electricity during the hours of daylight, and the output will vary with the position of the sun and cloud cover.  Likewise a wind turbine will produce its maximum (rated) power for a limited range of wind speed.  As the wind speed increases or decreases from there, the power output falls.

The difference between a conventional power station and a solar or wind farm is one small letter that is often dropped from news articles and statistics about this kind of renewable energy.  The letter ‘p’.
A solar panel power output is rated in watts-peak (Wp).  The electricity output of the panel is measured under very specific conditions of light and temperature – equivalent to a clear summer’s day at noon with the panel at 25C.  It is a useful measure to allow comparison of one product from another – it absolutely does not reflect any kind of average power output.

The scale of a solar installation such as a solar farm is the sum of all of the watts-peak of the solar panels used.  Again, a useful comparison between solar farms, but not between solar farms and conventional power stations.

Capacity Factors

The ratio of the energy output compared to that which would be expected if operating at full “nameplate” capacity the whole time is termed the Capacity Factor.
 
For the entire generating stock of power stations, it is necessary to be able to meet the peak electricity demands of the nation.  This means that at all other times, some of that generating capacity stands idle, resulting in an overall capacity factor between 50% and 60%. 

(Figures from Digest of UK Energy Statistics -DUKES table 5.10)

The energy output from a solar panel installation will depend upon its location, orientation and shading.  For well-situated PV installations in the UK, a rough guide is to expect around 850 kilowatt-hours (kWh) of energy for every installed kilowatt-peak of PV panels.  This corresponds to a capacity factor of around 10%.

Wind turbines at sea benefit from higher average wind speeds.  DUKES table 7.1 allows us to add the average capacity factor for wind energy.

Technology	Average Capacity Factor
Gas fired power station	60%
Wind Turbine (offshore)	30%
Wind Turbine (onshore)	22%
Solar PV (UK, S Facing)	10%

(Calculations can be viewed on this spreadsheet)

 All Watts are Equal...

Based on the above, 1 MW of gas fired power station produces the same annual energy output as 2MWp of offshore wind, 2.7 MWp of onshore wind or  6 MWp of solar photovoltaic panels.

The 650 MWp or so of solar photovoltaic panels installed in the UK during 2011 causing such panic in government circles is equivalent to a sixth of Little Barford power station.

How Much Electricity does the Average House Use?

Q: How Much Electricity does the Average House Use?

When putting the scale of a renewable energy development into context, it is common to state something like “this would provide electricity for” followed by a number of houses.  So what is the electricity consumption of a household?

One way to get at the number is to use the energy reporting from the Department of Energy and Climate Change (DECC).  Their Digest of UK Energy Statistics (DUKES) is a mine of information relating to energy.

Specifically, Chapter 5 deals with electricity and Table 5B shows domestic electricity sales for 2009.

Domestic sector electricity sales (Great Britain)              112,064 GWh

Number of domestic customers                                  26,987,000           (based on number of meters)

Dividing the first figure by the second gives a value for the average electricity use of a house.

A: 4,150 kWh/year

Q: How About Electricity Use per Person?

When you’re not at home, you’re probably still using electricity.  At work?  You need to power your computer, telephone, air-con, lights.  Sitting in the cinema munching popcorn?  Pay your share of the electricity to run the projector and the electricity to pop that corn.

On top of this, the goods you consume used electricity to extract, process, manufacture, package and transport them to the point where you buy them.

Domestic electricity use only accounts for 27% of the total, but the rest that is used in agriculture, industry and public administration is only there because you are.

Without getting bogged down worrying about the “balance of trade” in energy – that is that the UK imports more energy intensive goods and materials than it exports, it is possible to get an estimate for the electricity used per head of population as follows.

Total UK electricity consumption:             328,318  GWh                    (DUKES Table 5.1)

UK Population:                                           62.219 million                     (Google public data)

Again, divide one by the other to get electricity use per person

A: 5,276 kWh/year

Green Deal or No Deal

Selling Energy Efficiency

Government: “I will pay for you to make improvements to the energy efficiency of your house.  Don’t worry though – I’ll let you pay me back through your energy bills. The savings must exceed or equal the cost of the repayments and interest, so you may be better off.” 

 Homeowner: “Hmm.  Not the most persuasive sales pitch I’ve ever heard, but can you tell me more?”

Government: “Of course, we’re really excited about this initiative.  You’ll have to take time off work to be at home for the surveyor, and to let the installers into your home.  The installers may find stuff that needs fixing before they start work.  You know, wiring not up to current regulations, that kind of thing.  Of course, you’ll have to pay to put that right.”

Homeowner: “So I go through all this hassle and at the end of it my bills are about the same?”

Government: “Yes, clever isn’t it?”

Homeowner: “I’m not sure you’ve thought this through.”

Government: “Don’t worry about that, this programme is a main-stay of the government’s green agenda”

Homeowner: “Oh dear.”

The Energy Act 2011 passed into law on 19^th October, providing the legal framework for the Green Deal which is due to start in Autumn 2012.  Under the scheme, homeowners and tenants will be able to install energy efficiency measures such as loft and cavity wall installation, internal and external wall insulation, new doors, windows and boilers without paying the upfront costs.  Instead the costs and interest are spread out over a number of years and the payments are collected through energy bills.

DECC wants financing for the programme to come from commercial lenders and anticipates that because non-payment of energy bills would result in the householder being cut off, interest rates will be lower than for unsecured loans as people are more likely to keep up payments.

The re-payment of the loan is linked to the property rather than the individual, so if someone moves house, the new owners have to make the repayments, but also benefit from the energy saving measures.

The Golden Rule

A defining feature of the Green Deal is the so-called “Golden Rule”, that the annual charge does not exceed the value of the energy savings, leaving the housholder better off.  Results of our financial analysis of various energy improvements show that very few measures are likely to meet the rule at commercial lending rates.

 
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Measure	Cost	Approx. Annual Saving	Annual Repayment	Net Saving on Energy Bill	Meets Golden Rule?
Loft Insulation 100-270mm	£225	£25	£21.24	£3.76	Y
Timber floor insulation	£770	£60	£72.68	-£ 12.68	N
Cavity Wall Insulation	£475	£135	£44.84	£90.16	Y
Internal Solid Wall Insulation	£7,000	£445	£660.75	-£215.75	N
External Solid Wall Insulation	£11,200	£475	£1,057.20	-£582.20	N
New Boiler	£ 2,000	£150	£188.79	-£38.79	N

  The figures in the table were derived as follows:
Cost – source: Energy Saving Trust – where a range of values was given the mid-point was taken.
Approximate Annual Saving –  source: Energy Saving Trust – where a range is given, the mid-point was taken.
Follow the link in the table to see the source material.
Annual Repayment – assumed a 7% rate of interest, 20 year term.
Net Saving on Energy Bill – this is the Approx. Annual Saving less the Annual Repayment.

Check the workings here

The golden rule is only met by two measures – topping up loft insulation and cavity wall insulation.  The interest rate has been taken as 7%, which is an optimistic commercial rate considering that unsecured consumer loans are currently asking for around 10% APR.  In DECC’s Impact Assessment of the Green Deal, efficiencies of scale and learning are assumed for Solid Wall insulation, amounting to a 30% reduction in cost compared to those published by the Energy Saving Trust.

Even accepting DECC’s assumption that lower installation costs for solid wall insulation will emerge once installed in large numbers, internal solid wall insulation just meets the golden rule with 7% interest rate for a 25 year term (the maximum allowed), and external solid wall insulation only meets the golden rule with a very competitive 3% interest rate.

In the meantime, a trial by Sainsbury's demonstrates the challenge of selling the Green Deal.  When the supermarket offered 147,000 employees home insulation free of charge the offer was taken up by only 200 staff.

Of course if energy prices continue to rise, then the saving on the energy bill will rise too, making early adopters of the Green Deal look like investors of great foresight and acumen.  On the other hand, consumers may just choose to wait and see if energy prices reach a level that makes the Green Deal a deal worth the hassle.  Expect the Government to have to offer more incentives to sweeten this deal.

FIT to Burst - Government Adjusts PV Subsidy

“What’s that spine-chilling noise?  I’ll just check out the cellar.  The bulb has gone?  Let’s go anyway.”  As aficionados of horror movies know, the surprise that makes you jump out of your skin is the one you know is coming.  On Halloween 2011, the UK solar PV industry received just such a widely expected shock from the Department of Energy and Climate Change (DECC).

DECC has published a consultation document with proposals for changes to the Feed in Tariff (FIT) for solar photovoltaic systems (PV).  This scheme was created to encourage green technologies by rewarding individuals and businesses that install green electricity systems with payments for the units that they generate.

As discussed in an earlier Blog Post, the payments were fixed at a level that resulted in over-generous financial rewards.  A bubble inflated in the PV market as financial investors chased returns unavailable elsewhere in these fiscally challenged times.  The result was a growing financial commitment scary enough to make DECC want to hide behind the sofa.

It has been evident for quite some time that FIT payments were going to be adjusted downwards, and in a significant way.

The Changes

The consultation proposes a number of changes to the level and structure of the FIT scheme for PV.  The details are explained here, but in summary:

1.       There will be a 50% reduction to the payments for new systems joining the scheme.
2.       Even lower payments for organisations with installations at more than one location. 
3.       Only reasonably energy efficient buildings will qualify.

Analysis

DECC reckons that the new tariff level will result in a 4.5% financial return for a system installed in a good location.  However, PV prices are expected to fall further during 2012 as a global over-supply of PV panels corrects itself so returns for consumers investing in PV are likely to recover.
The creation of a new payment structure for organisations with installations in more than one location is aimed squarely at the “solar-for-free” or “rent-a-roof” companies.  These businesses approach householders or social landlords and offer to install PV systems free of charge on their roofs.  The company collects the payments, the resident gets to use the electricity generated (if they’re at home during the day) and there may even be a small fee for the use of the roof.  The consultation recommends a 20% lower tariff for these types of installation to reflect the greater economies of scale and lower installation costs for these companies.

Although the very significant change to the payment levels has provided a focus for the ire of solar PV companies, it is the third change that is likely to produce the most significant effect on the industry.

DECC are proposing that buildings with an energy performance certificate (EPC) level lower than ‘C’ would not qualify for the new payment levels.  The building owner then has the choice of accepting a much lower payment rate, or investing in their building to achieve the required energy efficiency.  DECC estimate that 86% of dwellings would not meet this criteria.  If this measure is implemented, DECC would have put a significant barrier in the way of the scheme uptake. 

Householders might have to pay for loft insulation, new boilers, and cavity wall insulation before installing a solar PV system.  What was a relatively painless and simple process has become more invasive and time consuming.
Social Landlords will have to upgrade the thermal performance of housing stock before moving on to more expensive renewable energy measures.

This  chiller contains a real twist in the tail, which is going to do more than anything to slow the uptake of PV.